Tuberculosis remains a severe global health problem. A better understanding of Mycobacterium tuberculosis, the bacterium responsible for this disease, will facilitate development of new anti-tuberculosis strategies. As in other bacterial pathogens, the secreted and surface-localized proteins of M. tuberculosis have important roles in virulence and in the development of host immunity. The long-term objective of this research is to define the systems responsible for exporting these proteins to their proper location and determine the role they play in M. tuberculosis pathogenesis. Our research has helped show mycobacteria to possess conserved protein export pathways: the general secretion (Sec) pathway and the twin-arginine translocation (Tat) pathway. We also identified a specialized system that is dedicated to a select subset of secreted and surface proteins. This SecA2-dependent export system is important to virulence as shown by the attenuated phenotype of a M. tuberculosis secA2 mutant in macrophages and mice. Macrophages infected with the secA2 mutant produce higher levels of pro-inflammatory cytokines and effectors. We hypothesize that the role of SecA2 in virulence is to limit host immune responses, possibly through modulation of MyD88-dependent pathways.
The specific aims of this proposal are the following. 1) Investigate the role of SecA2 in limiting host responses and promoting growth in macrophages by performing a global analysis of macrophage responses altered by SecA2 and testing the significance of the immunomodulation in macrophages and mice. 2) Identify SecA2-dependent proteins by quantitative proteomics and study the relationship between SecA2 and newly identified Dos regulated cell envelope proteins. 3) Characterize the mechanism of SecA2 export by identifying targeting domains in SecA2-exported proteins and by identifying proteins that work with SecA2 in export. The research in this proposal will improve our understanding of the role played by the SecA2 export system in M. tuberculosis pathogenesis and it will clarify the mechanistic basis of this new type of specialized export pathway. The results may reveal new approaches for disease intervention and facilitate construction of live mycobacterial vaccines with enhanced ability to export and present protective antigens.

Public Health Relevance

Tuberculosis is a severe world health problem. Secreted and surface-localized proteins of Mycobacterium tuberculosis, the causative agent of this disease, are important to virulence. The proposed research will define the systems that export these proteins to their necessary locations and determine the role they play in M. tuberculosis pathogenesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI054540-09
Application #
8509569
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Lacourciere, Karen A
Project Start
2004-01-15
Project End
2014-07-31
Budget Start
2013-08-01
Budget End
2014-07-31
Support Year
9
Fiscal Year
2013
Total Cost
$305,031
Indirect Cost
$97,739
Name
University of North Carolina Chapel Hill
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
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Swanson, Stephanie; Ioerger, Thomas R; Rigel, Nathan W et al. (2016) Structural Similarities and Differences between Two Functionally Distinct SecA Proteins, Mycobacterium tuberculosis SecA1 and SecA2. J Bacteriol 198:720-30
Feltcher, Meghan E; Gunawardena, Harsha P; Zulauf, Katelyn E et al. (2015) Label-free Quantitative Proteomics Reveals a Role for the Mycobacterium tuberculosis SecA2 Pathway in Exporting Solute Binding Proteins and Mce Transporters to the Cell Wall. Mol Cell Proteomics 14:1501-16
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Gunawardena, Harsha P; Feltcher, Meghan E; Wrobel, John A et al. (2013) Comparison of the membrane proteome of virulent Mycobacterium tuberculosis and the attenuated Mycobacterium bovis BCG vaccine strain by label-free quantitative proteomics. J Proteome Res 12:5463-74
Feltcher, Meghan E; Gibbons, Henry S; Ligon, Lauren S et al. (2013) Protein export by the mycobacterial SecA2 system is determined by the preprotein mature domain. J Bacteriol 195:672-81
Ligon, Lauren S; Rigel, Nathan W; Romanchuk, Artur et al. (2013) Suppressor analysis reveals a role for SecY in the SecA2-dependent protein export pathway of Mycobacteria. J Bacteriol 195:4456-65
Sullivan, Jonathan Tabb; Young, Ellen F; McCann, Jessica R et al. (2012) The Mycobacterium tuberculosis SecA2 system subverts phagosome maturation to promote growth in macrophages. Infect Immun 80:996-1006
Feltcher, Meghan E; Braunstein, Miriam (2012) Emerging themes in SecA2-mediated protein export. Nat Rev Microbiol 10:779-89
Bashiri, Ghader; Perkowski, Ellen F; Turner, Adrian P et al. (2012) Tat-dependent translocation of an F420-binding protein of Mycobacterium tuberculosis. PLoS One 7:e45003

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